Using UObjects as keys in arrays (even when TMap is marked as a UProperty) is dodgy. I’d look for another way of doing it.
Having said that, compile your code in debug mode and look at the array and the key values when the exception triggers a break point.
If you’re in the position where you are having to design code that maintains lists like that, it can be useful (and produce more optimal code) if you try and work out another way.
In this instance it could be more optimal (depending on your objectives) to just have your actors have a reference to the recipe maintainer class itself and not have it’s own list.